# Re: What databases have taught me

Date: 24 Jun 2006 18:16:40 -0700

Message-ID: <1151198200.922988.123690_at_u72g2000cwu.googlegroups.com>

mAsterdam wrote:

*> Marshall wrote:
**> >
*

> > But it would probably be better to provide an unambiguous

*> > definition of the problem. Perhaps a minimal example as well?
**>
**> How about:
**> Given A planar graph G, compute it's dual graph G'
**> (this takes out the real hard part, BTW:
**> given a graph compute if it's planar)
**>
**> If it is still unclear: just say what is the problem,
**> I'll do my best. (It's in my 1974 graph syllabus, and very rusty :-)
*

Okay.

First I need to know what a "graph" is. (Don't laugh.)

I think of the term as meaing "nodes and edges" but it appears for this paticular problem, we need faces as well. Yes/no? What are these faces? Are they collections of edges? Do the nodes have a position? If so, what must be the position of the nodes in the dual? If it's not specified, then how can we say the dual of the dual of the graph is the graph? Apparently it's okay to leave some things out, but it's not clear what.

Then I need to know what "dual" is. Etc.

In essence, I need a specification of the problem. All I've been given is the *name* of the problem, according to a nomenclature of a field of mathematics that I haven't studied, and pointers to vague sketches of the problem. That's not sufficient.

There are lots of important details to the problem that none of the references fill in. There are also no examples presented, which means that as I build an understanding of the problem, I have nothing to test it against.

The example can be quite primitive: just a triangle maybe.

Marshall Received on Sun Jun 25 2006 - 03:16:40 CEST